I had heard that too, but apparently we have both been taken in by an urban myth.
This is an explanation of how the myth might have arisen.
The urban legend ostensibly stems from the fact that the daddy long-legs spider is known to prey upon deadly venomous spiders, such as the [ame="http://en.wikipedia.org/wiki/Redback_spider"]redback[/ame], a member of the [ame="http://en.wikipedia.org/wiki/Black_widow_spider"]black widow[/ame] genus, [ame="http://en.wikipedia.org/wiki/Latrodectus"]Latrodectus[/ame]. By extrapolation it was thought that if the daddy long-legs spider could regularly kill a spider capable of delivering fatal bites to humans, it must be more venomous, and the uncate fangs were accused of prohibiting it from killing people. In reality it is merely quicker than the redback.
From
[ame=http://en.wikipedia.org/wiki/Pholcidae]Pholcidae - Wikipedia, the free encyclopedia[/ame]
and
Daddy Longlegs - Are Daddy Longlegs Venomous?

